Essential Cell Biology: Structures and Functions

Cell Biology Fundamentals

Cell: The structural and functional unit of living organisms; all cells originate from pre-existing cells through cell division.

Microscope: Uses a beam of electrons that collides with the preparation to produce high-resolution black and white images, allowing us to observe the internal structure of the cell.

Virus: Acellular entities containing RNA or DNA and protein. They lack their own metabolism, require a host cell to replicate, act as parasites, and alter the host cell.

Animal Cell Components

• Plasma Membrane: Selective and semi-permeable; composed of lipids, proteins, and carbohydrates.
• Smooth Endoplasmic Reticulum (SER): Connected tubes that manufacture lipids and metabolize alcohol.
• Ribosomes: Two sub-units that synthesize proteins by reading messenger RNA.
• Golgi Apparatus: Flattened sacs that package proteins and send them to their destination; they interact with lysosomes.
• Rough Endoplasmic Reticulum (RER): Connected sacs near the nucleus that synthesize proteins and carbohydrates.
• Nucleolus: The site where ribosomal RNA forms ribosomes.
• Nucleus: Contains genetic material (DNA).
• Nuclear Membrane: A double membrane that controls the substances entering and leaving the nucleus.
• Microtubules: Form the cytoskeleton and organize cell organelles.
• Mitochondria: Produce energy in the form of ATP through cellular respiration.
• Centrioles: Cylinders that form the mitotic spindle.
• Lysosomes: Contain enzymes to break down waste; possess a specific pH and membrane.

Plant Cell Structures

• Vacuole: Organelles containing waste, enzymes, oils, and pigments.
• Thylakoid: Contains chlorophyll within its membrane.
• Chloroplast: Oval, double-membrane organelle containing stacked crests (thylakoids) for photosynthesis.
• Cell Wall: Provides consistency and structural support to the plant cell.

Prokaryotic Cells

• Plasma Membrane: Selective barrier.
• Bacterial Wall: Structural support, lacks cellulose.
• Capsule: Protective layer surrounding the cell.
• Mesosome: Involved in cell division.
• Cytoplasm: Composed of cytosol and organelles.
• Locomotion: Microtubules, cilia, and flagella facilitate cell movement.

Genetics and Cell Cycle

Chromatid: A copy resulting from DNA duplication.

Centromere: The region where two chromatids are joined.

Chromosome: The total genetic structure contained within the nucleus.

Cell Cycle: The life of the cell consisting of two main phases:

• Interphase: The cell grows and replicates DNA. Phases include G1 (growth) and S (DNA replication).
• Cell Division (Mitosis): The process of distributing genetic material to daughter cells.

Stages of Mitosis

• Prophase: Nucleolus disappears, and the spindle apparatus forms.
• Metaphase: Chromosomes align.
• Anaphase: Chromatids separate.
• Telophase: The nuclear membrane reforms.

Asexual Reproduction

• Bipartition: Simple, fast division of a body into two daughter cells.
• Budding (Gemmació): A small daughter cell originates from the parent.
• Fragmentation: Development of new individuals from separated parts.